Boris Johnson has urged David Cameron to stop "pussyfooting around" over the need for a new airport for London, and claimed the prime minister has delayed the key decision because he is suffering from "institutional capture".

The London mayor attacked plans to postpone the decision on how to expand London's air capacity until after the next election in a post-Olympics interview in the London Evening Standard. He also did not rule out standing as an MP after his term as mayor ends in 2016.

Johnson revealed that when Cameron grabbed him in a hug during an Olympics photo opportunity, he whispered one word into the prime minister's ear: "Airport."

Calling for a "very powerful statement of ambition for London," Johnson said: "The government needs to stop pussyfooting around. I don't think you can rely on Heathrow. Even if the government was so mad and wrong to do the third runway or mixed mode [mixing take-offs and landings on the same runways] those solutions would rapidly run out of usefulness and time. I think George [Osborne] is actually very much up for big ideas like this."

Asked why Cameron seemed cautious, and whether this was a consequence of Whitehall, he replied: "I think there's a bit of institutional capture, yes. But it's a totally blind alley.

"The attempt to try and long-grass it for three years, into the other side of the election, is just not realistic. Totally mad and it won't work," he added, blaming the "institutional inertia of the government."

Johnson favours a new four-runway hub to be built in the Thames.

Asked what his plans were after standing down as mayor, Johnson said: "That's a good question. Four years is a long time in politics."

Rumours and speculation about his being a threat to Cameron were "incredibly flattering and bad for my ego". "But it's nonsense," he said. "I've got to get on with being mayor."

He was asked: if a seat came up after his mayoral term, would he take it? "I honestly don't know the answer to that question," he replied.

Johnson told the Standard: "The way to get business really motoring in the UK is to cut taxes, cut regulation, create the infrastructure and get behind it. That's what you should do."

He also said he had bold plans for a raised network of cycle paths built alongside railway lines, but said it was "very early stages" and "back-of-the-envelope stuff".